A fundamental problem in the neuroprotection field that remains unsolved is whether or not traumatically injured brain cells can be rescued from death. Essential concepts such as survival time and functionality of injured cells, and the "point of no return" from eventual demise have not been adequately explored in traumatic brain injury (TBI) models. Loss of plasmalemma integrity is a common feature of cellular injury and death in experimental TBI. Using propidium iodide (PI) to label cells with loss of plasmalemma integrity in vivo, we developed a PI pulse labeling protocol to follow the fate of injured brain cells after controlled cortical impact (CCI) in mice. Our findings suggest that although loss of plasmalemma integrity is a biomarker of fatal injury in many cells, a subset of PI+ cells may be rescuable by appropriate therapeutic agents. Based on these data, we propose three Specific Aims to test the central hypothesis that loss of plasmalemma integrity is a therapeutic target to rescue injured cells after TBI: Aim 1: Test the hypothesis that loss of plasmalemma integrity early versus late following controlled cortical impact is a biomarker of fatal versus rescuable injury, respectively. Aim 2: Test the hypothesis that loss of plasmalemma integrity is an active process mediated by TNF alpha and Fas receptors beginning early (minutes) after TBI, using in vitro and in vivo trauma models and mice or primary cortical neurons deficient in TNF/Fas. Aim 3: Test the hypothesis that restoration of plasmalemma integrity is a therapeutic target to rescue traumatically injured brain cells after CCI. Use poloxamer P188, a non-ionic amphiphilic triblock copolymer membrane resealing agent, and necrostatin-1, a specific inhibitor of TNF/Fas induced cell death, to reduce plasmalemma damage and acute cell death and improve functional outcome after CCI in mice. The proposed studies are intended to show that loss of plasmalemma integrity is a therapeutic target to rescue injured cells in patients with TBI. Work in this proposed project could impact public health by developing a new treatment for traumatic brain injury, and by developing tools that could assist researchers to better assess the potential value of therapeutic agents for brain and spinal cord injuries.